Thank you, Masterbk. I think my mistake was to have misunderstood Celia Davis. She said 'species of cherry (prunus spp)' have extrafloral nectaries on the petioles - so, not all prunus species as I've interpreted it. Cherry laurel (Prunus laurocerasus) and laurel (Laurus nobilis) have them on their leaves. I've just discovered that Stinkwood is also a prunus specie (Prunus africana), and their extrafloral nectaries are on the edges of the leaves, and I've planted some Myrobalan plums (or cherry plums - Prunus cerastifera) early this year, and I can't see that they have any extrafloral nectaries - so there seems to be a huge variety of positions of extrafloral nectaries on prunus species.

I'll try and find plum and cherry trees before the leaves fall.

Interesting point you mentioned about the bracken.
Kitta